ceph: support file lock on directory

Link: http://tracker.ceph.com/issues/24028Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/dir.c

@@ -1486,6 +1486,8 @@ const struct file_operations ceph_dir_fops = {
 	.release = ceph_release,
 	.unlocked_ioctl = ceph_ioctl,
 	.fsync = ceph_fsync,
+	.lock = ceph_lock,
+	.flock = ceph_flock,
 };
 
 const struct file_operations ceph_snapdir_fops = {